grievous errors of sysadministration

Those moments when you hit enter and then slap your forehead. Some notable examples: recursive removal of a directory under which various other boxes' filesystems were NFS mounted; attempts to transfer filesystems using tar with an absolute pathname, like this:

Never ever ever give the wildcard expression .* . This will cause more hurt than you could possibly imagine. Why? Because .* always matches .. . If you must do something unsavory in this vein, try .?* instead.